Re: [PATCH v3] drm/i915: Optimistically spin for the request completion

Tvrtko Ursulin
2015-03-12T17:32:31Z

On 03/12/2015 04:50 PM, Chris Wilson wrote:
> On Thu, Mar 12, 2015 at 04:41:10PM +0000, Tvrtko Ursulin wrote:
>> Yes I didn't mean that - but to have a boolean spinning-wait=on/off.
>> Maybe default to "on" on HZ=1000 with preemption, or the opposite,
>> something like that.
>
> I don't see the point in having the complication, until someone
> complains. In my defense, I will point to the optimistic mutex spinning
> equally having no configurable option. And since the idea is that you
> only hit this if you are abusing i915 (e.g. benchmarking, or you have a
> readback on the critical patch, or if we haven't implemented
> semaphores), I would rather fix those scenarios as they arrive rather
> than giving the user an option to break.

I simply pointed out a theoretical potential to burn more CPU on
servers. If you know that is unlikely or only theoretical that's fine by me.

But I'll say I was more convinced before you mentioned "until someone
complains" and "option to break". :)

Regards,

Tvrtko